Uppsala, Sweden Oct 18, 2022 (Issuewire.com) - In Africa, the Sahel/Savannah belt harbors diverse human groups of nomadic pastoralists and sedentary farmers. A new study found complex patterns of genetic diversity, admixture, and selection in populations from this large African region. The study now published in the journal Molecular Biology and Evolution was led by a team of researchers from Uppsala University, the Czech Academy of Sciences, and Charles University.
Drylands cover 60% of the African continent, and they are home to over 525 million people who depend on rainfed agriculture and livestock husbandry. The Sahel/Savannah belt, located south of the Sahara Desert and north of the tropical rainforests, is an important and large dryland region that is a crossroad between populations from different African and Eurasian regions. In this African region, domestication of the cereals developed independently from the Near East around 4.5 thousand years ago, and today is the residence of heterogeneous groups of sedentary farmers and nomadic pastoralists. In a new study, researchers generated and analysed genomic data (over 2.3 million genetic markers) of 327 participants from 14 Sahelian populations across the Sahel/Savannah belt (Senegal, Guinea, Chad, and Sudan).
The study unraveled complex patterns of genetic variation between and within populations from different regions in the Sahel/Savannah belt. For instance, “Fulani pastoralists in the Western part of the Sahel belt evidenced important amounts of genetic admixture between populations from Western Africa, North Africa, and the Middle East. In contrast, the Arabic-speaking populations in Chad and Sudan showed admixture between populations from Eastern Africa and the Middle East”, says Carina Schlebusch, Associate Professor in Human Evolution at the Department of Organismal Biology, Uppsala University (Sweden), who coordinated the study together with Viktor Černý, Professor in Anthropology at the Department of Anthropology and Human Genetics at Charles University (Czech Republic) and the Archaeogenetic Laboratory of Institute of Archaeology in Prague of the Czech Academy of Sciences.
Interestingly, one population in the Sahel belt showed completely different patterns of genetic diversity than other populations from the African continent. “The Rashaayda Arabic-speaking population from Eastern Sudan showed no evidence of genetic admixture between this population and other studied African populations. According to historical records, Rashaayda communities in Africa are descendants of recent migrants from Saudi Arabia”, says Viktor Černý. The researchers also found that this population has evidence of strong genetic isolation during the last few generations and small population sizes in the past due to a demographic bottleneck around 15 generations ago.
The study also investigated genomic regions that were candidates for selection. For instance, in the Bedik population from Senegal the candidate selection regions involved genes associated with several rare blood disorders. Other Western African populations showed candidate regions of selection that were associated with malaria genes, lactase persistence, and immune response. “In particular, a specific signal of exceptionally strong selection was detected in the Rashaayda Arab population and this region involves the CNR1 gene, which was previously associated with substance dependence and responses to chronic stress,” says Cesar Fortes-Lima, a Researcher in Population Genetics at the Department of Organismal Biology, Uppsala University (Sweden).
Therefore, the findings of the study improve our current knowledge of human diversity, population structure, migration, admixture, and adaptation of human populations in this part of Africa’s drylands, and shed new light on how selection may have influenced human adaptation to diseases, cultural factors, and environmental changes in Africa.
Funding: The study was funded by the European Research Council and the Grant Agency of the Czech Republic.
Reference: Demographic and selection histories of populations across the Sahel/Savannah belt. Cesar Fortes-Lima, Petr Tříska, Martina Čížková, Eliška Podgorná, Mame Yoro Diallo, Carina M Schlebusch, Viktor Černý. Molecular Biology and Evolution, 2022, msac209. https://doi.org/10.1093/molbev/msac209
For further information, contact:
Carina Schlebusch, Human Evolution Program, Department of Organismal Biology, Uppsala University (Sweden). Email: carina.schlebusch@ebc.uu.se
Viktor Černý, Department of Anthropology and Human Genetics at Charles University (Czech Republic) and the Archaeogenetic Laboratory of Institute of Archaeology in Prague of the Czech Academy of Sciences. Email: cerny@arup.cas.cz
Media Contact
Cesar Fortes-Lima, PhD cesar.fortes-lima@ebc.uu.se Human Evolution, Evolutionary Biology Centre, Uppsala University. Norbyvägen 18C, Uppsala, Sweden. http://katalog.uu.se/profile/?id=N18-1379
